2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2003 Marcel Moolenaar
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
32 #include <sys/types.h>
33 #include <sys/ucontext.h>
37 typedef void (*func_t)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
41 static void makectx_wrapper(ucontext_t *ucp, func_t func, uint64_t *args);
43 __weak_reference(__makecontext, makecontext);
46 __makecontext(ucontext_t *ucp, void (*start)(void), int argc, ...)
53 /* A valid context is required. */
54 if ((ucp == NULL) || (ucp->uc_mcontext.mc_len != sizeof(mcontext_t)))
56 else if ((argc < 0) || (argc > 6) || (ucp->uc_stack.ss_sp == NULL) ||
57 (ucp->uc_stack.ss_size < MINSIGSTKSZ)) {
59 * This should really return -1 with errno set to ENOMEM
60 * or something, but the spec says that makecontext is
61 * a void function. At least make sure that the context
62 * isn't valid so it can't be used without an error.
64 ucp->uc_mcontext.mc_len = 0;
68 /* Align the stack to 16 bytes. */
69 sp = (uint64_t *)(ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
70 sp = (uint64_t *)((uint64_t)sp & ~15UL);
72 /* Allocate space for a maximum of 6 arguments on the stack. */
76 * Account for arguments on stack and do the funky C entry alignment.
77 * This means that we need an 8-byte-odd alignment since the ABI expects
78 * the return address to be pushed, thus breaking the 16 byte alignment.
82 /* Add the arguments: */
84 for (i = 0; i < argc; i++)
85 args[i] = va_arg(ap, uint64_t);
87 for (i = argc; i < 6; i++)
90 ucp->uc_mcontext.mc_rdi = (register_t)ucp;
91 ucp->uc_mcontext.mc_rsi = (register_t)start;
92 ucp->uc_mcontext.mc_rdx = (register_t)args;
93 ucp->uc_mcontext.mc_rbp = 0;
94 ucp->uc_mcontext.mc_rbx = (register_t)sp;
95 ucp->uc_mcontext.mc_rsp = (register_t)sp;
96 ucp->uc_mcontext.mc_rip = (register_t)makectx_wrapper;
100 makectx_wrapper(ucontext_t *ucp, func_t func, uint64_t *args)
102 (*func)(args[0], args[1], args[2], args[3], args[4], args[5]);
103 if (ucp->uc_link == NULL)
105 setcontext((const ucontext_t *)ucp->uc_link);
106 /* should never get here */